1. Field of the Invention
The present invention relates to a method for effecting fast angulation changes of the C-arm of an x-ray system, as well as to a foot switch control for effecting such fast angulation changes.
2. Description of the Prior Art
X-ray systems are commonly used for medical diagnostic purposes as well as medical interventional procedures that have an x-ray source (x-ray tube) that emits x-ray radiation that penetrates an examination subject and is detected by a radiation detector disposed opposite to the x-ray source. The x-ray source and the radiation detector are movable relative to the patient, such as by being mounted on a rotatable C-arm or some other type of movement-facilitating mechanism. The angle that a center ray, emitted by the x-ray source and proceeding to the radiation detector, makes with respect to a predetermined axis, usually the vertical axis, is defined as the angulation of the x-ray system, and this angulation determines the viewing direction from which the x-ray exposure will be obtained.
An example of such an x-ray system is the AXIOM Artis dWA biplane angiography system commercially available from Siemens Medical Systems. In this known biplane system, a first x-ray source and a first radiation detector are mounted on a first C-arm, and a second x-ray source and a second x-ray detector are mounted on a second C-arm so that a 3D image can be constructed from the images obtained in two intersecting planes by the two C-arm-mounted systems.
Another example of such a system is the AXIOM Artis dTA System, also commercially available from Siemens Medical Systems. This is a monoplane system having a single universally adjustable C-arm on which the x-ray source and the radiation detector are mounted.
In examinations and procedures of the type described above, it is frequently necessary to bring instruments such as catheters, guide wires, stents, etc., into the target (imaged) region. For this purpose, generation of an x-ray image in which both the anatomy and the instrument itself are visible is very helpful. Monoplane systems, however, can supply only two-dimensional images, and therefore correctly positioning the x-ray system in space to generate a two-dimensional image that captures all of the desired information can be difficult for the physician.
In general, x-ray systems allow the angulation to be freely adjusted within certain limitations. The position of the x-ray tube and the radiation detector are changed relative to the patient, so that a substantially arbitrary viewing direction can be selected. The physician conducting the examination or the procedure can control the angulation to switch back and forth between multiple viewing directions, so that the physician can obtain the necessary spatial impression of the position of the instruments in space.
Different ways for allowing the physician to control the angulation, and operate other features of an x-ray system, are known, including levers, push buttons, computer interfaces and foot switches. A foot switch of the type used in the above commercially available systems is disclosed in U.S. Pat. No. 6,051,797, the teachings of which are incorporated herein by reference. That foot switch has a number of foot pedals thereon and is connected to a computerized control for the x-ray system so that each foot pedal of the foot switch has a permanently associated function that is activated, deactivated or controlled by a predetermined movement of the foot pedal such as pressing the foot pedal, releasing the foot pedal and, in the case of a pivotable foot pedal controlling the degree and direction of pivoting of that foot pedal.
In addition, it is common for one of the pedals to be associated with a “dead man” function, meaning that as long as this foot pedal remains pressed, a particular function, such as movement of the C-arm, is inhibited.
In the case of a system having a single x-ray and radiation detector (monoplane system), a typical procedure for changing the angulation includes stopping the radiation emission by releasing the radiation pedal, releasing the securing of the C-arm by releasing the “dead man” pedal, approaching the new angulation by operating a joy stick, and after achieving the target angulation, again pressing the radiation pedal to obtain images from the new perspective.
It is also known to associate pre-programmed positions of various components of the x-ray system with particular switch positions or switch actuations. Even with such pre-programmed assistance, changing the angulation still involves stopping the radiation emission by releasing the radiation pedal, making a selection from a list of the pre-programmed positions and selecting a target angulation, actuating a control element, such as the joy stick, to initiate automatic positioning of the system to the target angulation, and after achieving the target angulation, pressing the radiation pedal to obtain images from the new perspective.
As noted above, biplane systems are also known. In such systems, the positions of the respective planes of the two x-ray tube/detector pairs are automatically selected, and the physician only switches back and forth between obtaining images in the two planes. These systems, however, are significantly more expensive than monoplane systems. Moreover, the view is limited to two viewing directions, and access to the patient is made more difficult by the presence of the second x-ray system.